To identify the cities that may be at risk of a housing collapse, 24/7 Wall St. reviewed quarterly median home price data for 123 metropolitan statistical areas from real estate data firm ATTOM Data Solutions. We reviewed the 15 metro areas with the greatest percentage change in median home value from their pre-recession high to current levels. Ten-year population change came from the U.S. Census Bureau’s American Community Survey. The affordability ration — median home value-to-median household income — was calculated with 2017 data, also from the ACS. We excluded from consideration those markets with an affordability ratio higher than 3.61.